Looping problem faced since loops are not synthesizable. Any other way?

Hi can anyone please help me with this code i wrote for hc-sr04 (ultrasonic sensor)? I need to loop the process after 1 sec. Since i cannot use while or for loops because they are not synthesizable. Can someone tell me how i can loop this?

module usensor3 (trig, echo, distance_o,reset);
output trig, distance_o;
input clk, echo, reset;
reg  dist_counter=0;
reg  counter=0;
reg trig;
always @ (posedge clk)
	begin
			if (reset)
					begin
					counter<=0;
					dist_counter<=0;
					end
			else
				begin
					counter <= counter + 1;
					if (counter <= 500)              //10usec to initialize sensor
					trig<=1;                         // trig is set high
			
					if (echo)                        // sensing 5v at echo pin so echo pin is high
					begin
						dist_counter <= counter;      // counter value will be recorded in distance
						trig <=0;
					end
			
					if (counter<= 1900000)	  // maximum time of sensing any object is 38ms
					trig<=0;
			
				
					if (counter<= 5000000)      // wait 1 sec to begin again
					begin
					counter<=0;
					distance_o <=0;
					end
			
				   // How to start the whole cycle again
				
			end
	end	
			
assign distance_o = (dist_counter * 340) << 1; //The velocity of the ultrasonic burst is 340m/sec in air
endmodule